But Trump’s use of the slur during an event meant to honor Native Americans, in the Oval Office of the White House, was unprecedented.

During an appearance on MSNBC shortly after the event, Warren reacted to Trump’s comments, saying, “It is deeply unfortunate that the President of the United States cannot even make it through a ceremony honoring these heroes without having to throw out a racial slur.”

“Look, Donald Trump does this over and over thinking someone he’s going to shut me up with it — it hasn’t worked in the past, it’s not going to work in the future,” she added.

If Trump’s remarks weren’t troubling enough, Monday’s Oval Office event with the Native American code talkers was held in front of a portrait of Andrew Jackson, whose Indian Removal Act led to the deaths of 4,000 Cherokee and Creek tribe members.

In March, Trump became the first president since Ronald Reagan to visit Jackson’s Tennessee home.

Spokesman for alliance of Native American tribes says Trump's commentary "smacks of racism" and president should "stop using our historical people of significance as a racial slur against one of his opponents."https://t.co/iBTxWWxLwF